The present application claims priority under 35 USC 119 to Japanese Patent Application No. 2001-252169 filed on Aug. 22, 2001 the entire contents thereof is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a balancer for an engine.
2. Description of Background Art
Japanese published examined Patent Application No. Hei 2-118227, discloses a balancer for an engine that is provided with a balance weight at both ends of a balancer shaft. A balance weight positioned on the side of a balancer gear, that is separate from the balancer gear, is formed so that the outer diameter is smaller than the root circle diameter. The balance weight is arranged inside the balancer gear.
It is also conceivable that a balancer gear may be made to have the form of a balance weight. However, since such a gear has an anomalous outline, it has a tendency for the precision of the gear to be deteriorated by distortion after heat treatment. When the balance weight is made separate from the balancer gear, the above-mentioned problem can be solved. However, in the case of a balance weight having a smaller diameter than the root circle diameter, the width of the balance weight is increased to secure a sufficient unbalance amount. This increases the size of the engine with an increase in the weight.
An object of the present invention is to provide a balancer that can acquire an unbalance amount efficiently and can contribute to the miniaturization and the reduction in the weight of the engine.
To solve this problem, the present invention provides a balancer of an engine that is configured so that a balance weight that is provided on a balancer shaft parallel to a crankshaft of the engine is rotated by a balancer gear interlocked with the crankshaft and includes the balance weight that is formed as another member the diameter of which is larger than the root circle diameter of the balancer gear and is jointly fastened to the side of the balancer gear.
The present invention includes the balancer gear that is fitted to the balancer shaft via a spline, a fitting hole is provided to the end on the side of the balancer gear of the balancer shaft and an accessory driving member is fitted into the fitting hole.
The present invention provides a balancer for an engine wherein a balance weight is provided to both ends of a balancer shaft parallel to a crankshaft of the engine which is configured so that the balance weights are rotated by a balancer gear interlocked with the crankshaft and includes a balancer driven gear that is provided to one end of the balancer shaft. A balance weight is integrated with the other end a gear for driving an accessory that is provided to the inner side of the balance weight.
According to the present invention as the outer diameter of the balance weight is constructed to be larger than the root circle diameter of a balancer driven gear in a structure where a separate balance weight is formed outside the balancer driven gear rotated by the transmission of power from a balancer drive gear fixed to the crankshaft, a sufficient unbalance amount can be efficiently secured. As a result, the width of the balance weight can be minimized. Thus, an increase in the width of the engine is inhibited and the engine can be lightened and miniaturized.
Also, as the balance weight is separate from the balancer driven gear, the balance weight the diameter of which is made larger than the root circle diameter of the balancer driven gear can be arranged very near to the balancer driven gear. In case a balance weight having such a large diameter is integrated with a balancer driven gear, the teeth of the balancer driven gear cannot operate. However, according to the present invention such a manufacturing problem is not caused. Thus, the balance weight can be easily fixed to the balancer shaft by jointly fastening the balance weight to the side of the balancer driven gear.
According to the present invention, as the balancer gear is fitted to the balancer shaft via a spline, the fitting hole is provided to the end on the side of the balancer gear of the balancer shaft and the accessory driving member is fitted into the fitting hole, the accessory can be coaxially driven by the balancer shaft. Since a large space is not require to couple the accessory driving member though the balancer gear and the balancer weight are provided to the end of the shaft, the engine can be miniaturized.
According to the present invention, as the balance weight is provided on both ends of the balancer shaft, the balancer driven gear is provided to one end, the balance weight is integrated with the other end and the gear for driving the accessory is provided to the inner side of the balance weight, the gear for driving the accessory can be provided very near to the balance weight and it does not require a large space to attach the gear for driving the accessory. In addition, on the side of one end of the balancer shaft on which the balancer driven gear is provided, the driving shaft of one accessory is coaxially connected, the driving shaft of the other accessory is turned in parallel with the balancer shaft via the gear for driving the accessory on the side of the other end and the other accessory can also be arranged near one accessory. Therefore, the engine can be miniaturized.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.